Methods1) Heat the oil in a large saucepan. Add the onion to the pan and cook until softened. Add the garlic, ginger, cumin, cinnamon and cayenne and cook for a further 2 minutes. Add the chopped tomatoes and sweet potatoes to the pan, stir well and cook for another 5 minutes.
2) Add the peanuts and stock to the pan and bring to the boil. Reduce the heat and simmer for 30 minutes. Blend in batches until smooth. Return to the pan and stir in the peanut butter until it melts.